java mcp message endpoint error

[a67793581]

Expected Behavior

The implementation should properly handle cases where messageEndpoint already contains a protocol and host to avoid incorrect concatenation.

Current Behavior

Currently, the Java MCP SDK does not correctly handle messageEndpoint. Instead of properly resolving the full URL, it simply concatenates messageEndpoint with the base URL as a raw string. This results in malformed URLs, such as: http://localhost/mcphttp://localhost/mcp/message

Context
mark3labs/mcp-go#76 (comment)
Here are the references:

https://github.com/modelcontextprotocol/java-sdk/releases/tag/v0.8.1

public Mono<Void> sendMessage(McpSchema.JSONRPCMessage message) {
    if (this.isClosing) {
        return Mono.empty();
    } else {
        try {
            if (!this.closeLatch.await(10L, TimeUnit.SECONDS)) {
                return Mono.error(new McpError("Failed to wait for the message endpoint"));
            }
        } catch (InterruptedException var5) {
            return Mono.error(new McpError("Failed to wait for the message endpoint"));
        }

        String endpoint = (String)this.messageEndpoint.get();
        if (endpoint == null) {
            return Mono.error(new McpError("No message endpoint available"));
        } else {
            try {
                String jsonText = this.objectMapper.writeValueAsString(message);
                HttpRequest request = HttpRequest.newBuilder().uri(URI.create(this.baseUri + endpoint)).header("Content-Type", "application/json").POST(BodyPublishers.ofString(jsonText)).build();
                return Mono.fromFuture(this.httpClient.sendAsync(request, BodyHandlers.discarding()).thenAccept((response) -> {
                    if (response.statusCode() != 200 && response.statusCode() != 201 && response.statusCode() != 202 && response.statusCode() != 206) {
                        logger.error("Error sending message: {}", response.statusCode());
                    }

                }));
            } catch (IOException var6) {
                return !this.isClosing ? Mono.error(new RuntimeException("Failed to serialize message", var6)) : Mono.empty();
            }
        }
    }
}```

[jpfortier]

Hi, do you know if there is a workaround? Is this due to a misconfiguration on my part? (seeing this error on a call that worked yesterday)

[a67793581]

Hi, do you know if there is a workaround? Is this due to a misconfiguration on my part? (seeing this error on a call that worked yesterday)
Because the official Java MCP SDK does not open related options, we can only ensure that all other language MCP SDKs are configured to be compatible with the Java MCP SDK.

[Mukamik]

I wonder if the InterruptedException is overly broad. Is it possible that a simple misconfiguration (like a port conflict) could be caught by this exception?

java-sdk/mcp/src/main/java/io/modelcontextprotocol/client/transport/HttpClientSseClientTransport.java

Line 406 in 0069c97

catch (InterruptedException e) {

[chemicL]

It looks like this was resolved by #150. Please re-open if that's incorrect.